In a multi-racial cohort of Australian children, 0.01% atropine eyedrops were safe, well-tolerated and had a modest myopia control effect, according to a single-centre, double masked, randomised, placebo-controlled trial conducted in Western Australia.
The West Australian Atropine for the Treatment of Myopia (WA-ATOM) study, was led by Dr Samantha Sze-Yee Lee and Professor David Mackey, and published in Clinical and Experimental Ophthalmology. Results clear the way for further studies to compare different dosages of atropine. Additionally, the results will be combined with those from similar studies in Ireland and the United Kingdom, facilitating a large and prospective independent participant meta-analysis of low concentration atropine efficacy for myopia control in Western populations.
The WA-ATOM study is the first to test the hypothesis that nightly instillation of 0.01% atropine eye drops is a safe and effective myopia-control therapy in a multi-racial cohort of children (~50% European, aged six to 16) reflective of the broader Australian population.
Other studies – the ATOM study in Singapore, the Low Concentration Atropine for Myopia Progression (LAMP) study in Hong Kong, and the Indian ATOM study, have all observed myopia control effect with low dose atropine in South and East Asian children. The LAMP study also compared concentrations of 0.01%, 0.025% and 0.05%.
Enrolled participants for the WA-ATOM study completed their baseline visit between June 2017 and December 2019. At each subsequent visit, from six to 24 months, measurements were recorded for ocular biometrics (anterior chamber depth, central corneal radius, lens thickness and central corneal thickness); pupillary measures (constriction latency, constriction velocity, dilation velocity, and amplitude) and other ocular measures (distance and near best corrected visual acuity, accommodative amplitude and stereoacuity). A questionnaire was also used to record information on each child’s experience using eye drops and any adverse events. Parents and children reported both the placebo and atropine 0.01% eyedrops were well-tolerated, with >90% of parents/caregivers in both groups saying, “their child did not seem to mind the eyedrops and that the eyedrops did not affect their child’s activities, including near work, outdoor activities and learning”.
While previous studies have shown 0.01% atropine eyedrops slowed progression in East or South Asian children, but had little impact on axial length, this study found a modest myopia control effect at 12 months, however this effect was not significant at 24 months when compared to the control group.
The researchers propose this may be due to one (or all) of three reasons:
- faster progressing myopes in the control may have withdrawn,
- myopia progression slows with age, and this may have influenced the control group who were, on average, one year older than the atropine group, and
- In line with other studies, it is accepted that the greatest slowing of myopia will be achieved in the first year of treatment.
The authors reported that 0.01% atropine eyedrops were more effective in slowing myopia progression and axial elongation in participants of European or other/mixed ancestries than East or South Asian children. They suggested this may be due to either a small sample size or because low concentration atropine eyedrops may not be as effective in slowing myopia progression in Asian children living in Australia relative to those living in Asia. It is unclear why a smaller effect was found in Asian children living in Australia compared to those living in Asia. In a previous article, Lee et al.1 suggested that a difference in the magnitude of the effect could be related to environmental difference, where children in Australia spend more time outdoors.
Anterior chamber depth (ACD) significantly increased in both the atropine and placebo groups; however, the atropine group had a larger ACD increase, despite slower axial elongation in that group than the placebo group. This is likely because cycloplegic eyedrops, including atropine, cause the crystalline lens to move posteriorly as the ciliary muscle relaxes.
Ocular effects, including reduced pupillary constriction and accommodative amplitude, were small and not associated with complaints of photophobia or blurring of near vision. Best corrected visual acuity (BCVA) was significantly better in the atropine group at most study visits relative to baseline, and there was no difference in change in near BCVA or stereoacuity between groups.
With this study alleviating concerns about side effects of low-concentration atropine in Australian children, the researchers say it may now be scientifically and ethically viable to move ahead with non-inferiority myopia control trials, rather than placebo or single-vision lenses as controls.
Future studies could explore whether slightly higher concentrations of atropine, for example, 0.02%, may still be tolerated in Australian or European children while having greater efficacy.
Reference
Lee, SSY, Mackey, DA, Lingham, G, et al. Western Australia Atropine for the Treatment of Myopia (WA-ATOM) study: Rationale, methodology and participant baseline characteristics. Clin Experiment Ophthalmol. 2020; 48: 569– 579. https://doi.org/10.1111/ceo.13736
